The following
two verses are the ones that raise the questions concerning the difference
between "spirit and soul":

"May God himself, the God of peace, sanctify you through and through.
May your whole spirit, soul and body be kept
blameless at the coming of our Lord Jesus Christ." [1 Thessalonians 5:23]

"The word of God is living and active. Sharper
than any double-edged sword, it penetrates even to dividing
soul and spirit, joints and marrow; it judges the
thoughts and attitudes of the heart." [Hebrews 4:12]

In these two
verses the word translated "spirit" is the Greek word "pneuma" which means "a
current of air, i.e. breath (blast) or breeze" which by analogy refers to a
human "spirit" the rational "soul." The word translated "soul" in the verse is
the Greek word "psuche" which means "breath" and by implication "spirit." So
the use of the two words does not indicate that the immaterial part of man could
be divided, but rather are used simply for emphasis. There are not three parts
to humans (body, soul, and spirit) but only two (body and "soul or spirit").
Throughout Scripture we see the two terms "spirit" and "soul" used
interchangeably:

"We have this hope as an anchor for the
soul, firm and secure. It enters the inner
sanctuary behind the curtain..." [Hebrews 6:19]

"Dear friends, I urge you, as aliens and
strangers in the world, to abstain from sinful desires, which war against your
soul." [1 Peter 2:11]

"....that righteous man, living among them day
after day, was tormented in his righteous soul by
the lawless deeds he saw and heard." - [2 Peter 2:8]

In these three
verses we find the word translated "soul" is the Greek word
"psuche" = breath (by implication spirit). So God
is referring to that part of us which is our spirit, the eternal part He put
into us when we were conceived (made alive)

"....the LORD God formed the man from the dust
of the ground and breathed into his nostrils the breath of
life, and the man became a living being." [Genesis 2:7]

It is not "air"
that made us alive but the "spirit or our soul" that caused us then to start
breathing the air. So we have only two parts: the body, and the spirit (or
soul). The words are interchangeable. In the verses above the translators
could have just as easily chosen to use the word "spirit" just as well.

Now, we even see the same word "psuche" which is translated "spirit" or "soul"
also translated "mind" in the next verse:

"All the believers were one in heart and
mind. No one claimed that any of his possessions
was his own, but they shared everything they had." [Acts 4:32]

The concept is
that our "mind" is really our "spirit/soul" ....not the brain matter, but what
is operating on and through the brain: our soul. Some honestly feel that our
"soul" or "spirit" actually resides in our heads, because the brain is located
there.

Now, to show how important it is to know which Greek word is being use to gain a
proper understanding, look at the next verse:

"Love the Lord your God with all your
heart and with all your soul
and with all your strength and with all your mind...."
[Luke 10:27]

The word for
"heart" here is "kardia" = "the
thoughts or feelings (mind)" It does not refer to the flesh of the heart that
pumps blood, but really our "mind" in the sense of our "soul" or "spirit." The
word translated "soul" in the verse is "psuche" (breath). But the word
translated "mind" here is not referring to our "soul or spirit" for the Greek
word used is "dianoia" which refers to our "deep thoughts" that is, the exercise
of our minds. So the verse used "heart and soul" for emphasis, since they
really refer to the same thing: the "spirit," and then adds that we are to love
our God with our actual thoughts.

So in summary,
the "soul" and the "spirit" are one and the same, just two words meaning the
same thing: the eternal immaterial part of each person. I might note that when
a person becomes a Christian, the Holy Spirit comes and resides inside our
"soul/spirit."